XP "holdouts" might well be very encouraged that Firefox 4 and probably Google Chrome will work with GPU acceleration on XP.

Some certainly will but MS is also sending a strong message which is that they are moving away from XP.

A lot of software developers might come to realise that if they target Qt for the GUI and system interfaces, and write their applications in C++, D, Python or even Java or Google Go, then they can target not only Win 7 and Vista users, but also XP users, Mac OSX users and Linux users.

Not that simple because of existing skill sets, productivity rates and features specific to .net.

No IDE is up to par with Visual Studio and there are additional benefits to working exclusively with .net.

Qt still has issues with OSX that need to be resolved but in a few years I think it will provide some good competition.

Alternatively, one might soon be able to write cross-platform DX10/DX11 games due to a state tracker for DX10/DX11 becoming available for use with Gallium3D drivers on linux.

Are you really suggesting an alternative that doesn't exist yet?

If one simply avoids .NET, and instead uses cross-platform frameworks, these days one can write great cross-platform applications and hence be in a position to sell one's software to a much wider market than just Win 7 and Vista.

Sounds good in theory but you underestimate the amount of work required to target multiple operating systems. There is no "write once, run anywhere" framework but Qt is getting there.

" XP "holdouts" might well be very encouraged that Firefox 4 and probably Google Chrome will work with GPU acceleration on XP.

Some certainly will but MS is also sending a strong message which is that they are moving away from XP. "

Likewise, many Windows users are sending a strong message that they wish to stay with XP. If Microsoft do not wish to support that userbase, as seems to be the case, then that is a sizeable userbase to leave behind.

Since Microsoft has effectively signalled that they are not going to write new update versions to target the XP platform any longer, this userbase is effectively a gift from Microsoft (we won't compete to this market) to any developers who might wish to accomodate them.

" A lot of software developers might come to realise that if they target Qt for the GUI and system interfaces, and write their applications in C++, D, Python or even Java or Google Go, then they can target not only Win 7 and Vista users, but also XP users, Mac OSX users and Linux users.

Not that simple because of existing skill sets, productivity rates and features specific to .net. No IDE is up to par with Visual Studio "

Debatable. Very debatable. A lot of software is written, very productively, using IDEs that are not Visual Studio. Visual Studio is almost alone amongst powerful IDEs these days in being single-platform-only.

and there are additional benefits to working exclusively with .net.

Debatable about the benefits. There is a huge penalty to working exclusively with .net in that your application will likely be constrained to a smallish market (those running Vista and Win 7) compared with a much larger market (Vista, Win 7, Win XP, OSX and Linux) that rival applications could sell to.

"Alternatively, one might soon be able to write cross-platform DX10/DX11 games due to a state tracker for DX10/DX11 becoming available for use with Gallium3D drivers on linux.

Are you really suggesting an alternative that doesn't exist yet? "

Not really, but some developers might be stuck with DirectX rather than openGL, and be glad that the market they can sell to might one day expand (provided they don't use .NET now).

" If one simply avoids .NET, and instead uses cross-platform frameworks, these days one can write great cross-platform applications and hence be in a position to sell one's software to a much wider market than just Win 7 and Vista.

Sounds good in theory but you underestimate the amount of work required to target multiple operating systems. There is no "write once, run anywhere" framework but Qt is getting there. "

There is indeed a "write once, run anywhere" framework. Actually there are a few: java, Qt, GTK - this is why we have OpenOffice, VLC/Inkscape and Firefox/Chrome respectively, as examples, that are already cross-platform applications. Qt has already "got there" for a number of cross-platform applications that exist today. More and more applications are targetting cross-platform frameworks (because one can sell to a much wider market), and Qt is one of the the easiest but still powerful options for doing this.

It is no longer nearly as difficult as it used to be to target cross-platform these days, as long as one avoids .NET.

Debatable about the benefits. There is a huge penalty to working exclusively with .net in that your application will likely be constrained to a smallish market (those running Vista and Win 7)

All versions of .net work with XP. There are however some feature and development limitations related to XP that I don't want to get into especially since you haven't read the basics. In a nutshell applications get stuck at XP level for .net devs thanks to XP holdouts but even with those limitations the productivity benefits typically outweigh being unable to target OSX. For enterprise it is an easy choice where every computer runs Windows.

I already said that in a few years Qt will provide some serious competition, why not be patient and wait? The market has not shifted to .net out of conspiracy. Java on the desktop just plain sucks and Qt has only been decent recently and still has some native integration issues in OSX that need to be resolved. Once Qt apps are indistinguishable from native apps then you will see greater adoption.

You seem to not realize that I am not wed to .net or msft. I used to work with Java and if the world switched to Qt I would shrug and continue writing code. However a major switch does not make sense at this point but in a few years Qt will have a much wider appeal. There are plenty of factors working in favor of Qt, your advocacy efforts are not needed.

There is indeed a "write once, run anywhere" framework. Actually there are a few: java, Qt, GTK - this is why we have OpenOffice, VLC/Inkscape and Firefox/Chrome respectively, as examples, that are already cross-platform applications.